Volcanoes. 265 



open a passage in the side of the mountain than to elevate the 

 mtumescent mass to the summit. In the last eruption of Te- 

 neriffe, a lateral opening was formed ; and, according to a cal- 

 culation by M. Daubuisson, it would have required a force 

 equivalent to a thousand atmospheres to have raised the mass 

 of lava to its elevated crater. 



Of volcanoes in the phase of moderate activity, the best 

 example to which we can refer is that of Etna, between the 

 years 1804 and 1818. Segnio Maria Gemmellario {Jour. 

 Science, vol. xiv. p. 322.) has given us a very interesting view 

 of the successive changes which were observed, through a 

 meteorological journal kept at Catania. 



On the 9th of February, 1804, there was a sensible earth- 

 quake : Etna smoked 97 days, but there was no eruption nor 

 any thunder. 



On the 3d of July, 1805, there was an earthquake: Etna 

 smoked 47 days, and emitted flame 28 days. There was an 

 eruption in June, but no thunder. 



There were earthquakes on the 27th of May, and 10th of 

 October, 1806. The mountain smoked 47 days, flamed 7, 

 and detonated 28 : little thunder. 



On the 24th of February, and 25th of November, 1807, 

 there was an earthquake. Etna smoked 59 days. Little 

 thunder. 



In August, September, and December, 1808, earthquakes 

 were frequent. Etna smoked 12 days, flamed 102, and often 

 detonated. Thunder storms were frequent. 



From January to May, and during September and Decem- 

 ber, 1809, there were 37 earthquakes. The most sensible 

 shock was on the 27th of March, when the mountain ejected 

 lava on the western side. This eruption lasted 13 days; and 

 part of the Bosco de Castiglione was injured. The mountain 

 smoked 152 days, flamed 3, and detonated 11. Little thunder. 



On the 16th and 17th of February, 1810, there were four 

 earthquakes. On the 27th of October, Etna suffered an 

 eruption on the east side, and the lava flowed into the Valley 

 del Bue. There were about 20 thunder storms. 



1818, no earthquakes. The mountain continued to eject 

 lava from the east until the 24th of April. At this time the 

 mount S. Simon was formed. No thunder. 



3d and 13th of March, 1813, earthquake. The mountain 

 smoked 28 days. On the 30th of June and 5th of August, 

 S. Simon smoked. There were 21 thunder storms. 



On the 3d of November, 1814, there was an earthquake, 

 preceded by a discharge of sand from that part of the moun- 

 tain called Zoccolaro. There were 12 thunder storms. 



